As is easily appreciated, there are many uses for compressed gas which are better performed if the gas is clean and dry. For example, moist air used in conjunction with pneumatic instruments, controls and tools can cause corrosion and malfunction; or if moist air is used when spraying paints and coatings, surface blemishes may result. In such applications, it is well known to utilize compressed air drying systems comprising two beds of a desiccant material. One bed adsorbs moisture from the compressed gas at operating pressure, while the other bed is in a regeneration phase, usually at atmospheric pressure. The size of the pipe used in high capacity drying systems can be three or more inches in diameter, with rotating plug-type and ball-type valves being widely used in conjunction with such large drying systems. It will be appreciated that such valves must be quite bulky and expensive to accommodate the flow without undue pressure drops and also require proportionately large and expensive actuators. In addition, the severe conditions, which range from moist, inlet air to very dry and possibly dusty purge and effluent air, have been found to adversely affect the life and operation of such valves.
Thus, it is the principal object of the present invention to provide valves specifically designed for use in desiccant drying systems and which are less bulky and expensive than many.
A further object is to provide a family of valves for use in desiccant drying systems wherein each of the different types of valves utilizes common or similar components.